I need to make my images broadcast safe - there were a few hot spots on our actors' heads where the light was set too bright. I know that a yellow exclamation mark indicates that either the luminance or chroma is a problem, but how do I know which is the problem? And how do I fix it?
You can either apply a 3-way color corrector filter and manually reduce the highlight and chroma levels, or you can apply a broadcast safe filter. Some have found that the broadcast safe filter is unreliable and may not always produce broadcast-safe levels. It's probably safer to do it manually. Levels often change after rendering, so after applying the CC filter and corrections, render and re-check levels.
Specifically, double-click your video track to highlight and select it, then go to filters?Video filters> Color correction and there you'll find the broadcast safe and the 3-way, perhaps more, depending on the plug-ins you've added.
You should make visible your waveform and vector scope display when you do this, so you get a better idea where the hotspots and such are.